The Federal
Communications Commission (FCC) specifies the rules for
operating in the unlicensed 2.4 GHz spectrum. The largest
governing concern is harmful interference with authorized
services and must work around any interference that may be
received from phones, microwaves or other RF devices.
The FCC mandates that a device must operate in one of
two ways in the 2.4 GHz ISM band:
• Frequency Hopping Spread Spectrum (FHSS). The frequency
changes in a pseudo-random manner based on a predefined
code.
• Direct Sequence Spread Spectrum (DSSS). The data signal
is broken up into sequences and transmitted to the receiver,
which reassembles the sequences into the data signal.
Future versions such as 802.11g may adopt OFDM if the
FCC decides to support it and the industry can agree to rally
behind it. However, at the time of publishing this book, these
are two very big “ifs.”
It is estimated that more than 7.8 million wireless LAN
chipsets were produced in 2000. A similar number is expected
in 2001. Sales are growing from almost $400 million in 2000
to $1.2 billion by 2005. Costs have dropped during 2001, causing
widespread usage in homes and enterprise systems.
However, 2002 will see the release of more Home RF and
802.11g products also. Parks Associates estimates that, while 5
percent of U.S. households currently have a PC network in
place, as many as 15 percent will have one in five years. Of
that, wireless networking will account for 40 percent of all
those home networks.